Dear Bristolweb,
in some way it still does. Page Rank as you know is being build be gathering links to your websites. PR from the linking website to your own flows over a little. The same goes with Domain Authority and other metrics.
The more people "vote" on your website the better Google will have to like your site because people told Google this is what we would like to see.
So:
quality linking to your websites increases page rank - > more quality links improve your metrics -> more quality links improve your position in Google.
If you really want o improve your pages rank or page rank or whatever name you want to use you could commit yourself to a on-line community asking question, answering questions about the subject of your website. Linking to it from the community helps a lot and also spend time on link building. Use the tools provided by SEOMoz to check out your competitors and make sure you get a link on that page. It could only help not harm your site (not completely true but it's all about the essence in here).
So to sum up my advise:
Yes, PR of pages rank is a (very small) factor in the Google Algorithm so it's still important.
Should you focus on it? In a way: Yes. As I already explained PR is mainly build on the number of "Votes" that go to your websites. So getting more Votes improves your PR and improve the amount of traffic (when you get quality votes) which in turn is a factor in the Algorithm.
Focus on gaining good quality links to your website. It will help!